1. Field of the Invention
The invention relates to electronic communication. More particularly, the invention relates to wireless communication repeaters.
2. Description of the Related Art
Wireless communication systems allow users to remain connected to a network without being tethered by a wire line. Mobile stations often connect to a communication network via fixed base stations. Multiple base stations may be distributed across a geographic region to enable a mobile station to connect with the communication network throughout the region. However, because the communication between base stations and mobile stations occurs over wireless communication links, many factors can affect the signal quality. For example, the signal transmitted from a base station to a physically distant mobile station at an edge of a coverage area served by the base station may be severely attenuated. Additionally, obstructions, such as buildings, terrain, and trees may severely attenuate a wireless communication link between a mobile station and a base station. Obstructions that result in coverage holes are common in dense urban environments. Thus, an ideal coverage area served by a base station may, unfortunately, include one or more holes in the coverage area.
One manner of extending the coverage area of a base station or of filling in coverage holes is to employ wireless communication repeaters. The repeaters operate as extensions to a base station to allow increased coverage without the cost or complexity associated with adding more base stations to the communication network. A repeater can receive a transmit signal from a base station and retransmit it, effectively repeating the received transmission. The repeater can also receive a signal transmitted by a mobile station and retransmit it to the base station.
Using repeaters to extend the coverage areas of a base station typically does not pose a problem in systems where timing or placement of the signal sources is not a critical component of the communication link. However, in more complex communication systems, signal timing and the position of the originating source are critical.
For example, in a Time Domain Multiple Access (TDMA) communication system the time slot assigned to a communication link is related to the time delay for a signal to traverse the path from the transmitter to the receiver. A receiver in a TDMA system would thus need to know if the received signal originated from a base station or a repeater.
Additionally, some wireless communication systems, such as wireless telephone systems, implement position determination. Indeed, in the United States, enhanced emergency wireless service having the capability of determining the location of a handset has been mandated for wireless phone providers. Wireless service providers, in conjunction with equipment manufacturers, have devised a variety of position determination systems that are able to provide the location of a mobile device, such as a portable handset.
However, position determination techniques used in wireless phone systems often use the position of the stationary signal source in determining the position of the mobile station. A functional block diagram of a typical wireless communication system 100 is shown in FIG. 1. The wireless communication system 100 includes at least one base station 102 in communication with a repeater 112. A wired communication link 110 is shown coupling the base station 102 to the repeater 112. It is also common for a wireless communication link to be used to couple the base station 102 to the repeater 112. A mobile station 150 is shown in communication with the repeater 112.
The repeater 112 merely acts as an intermediary between the base station 102 and the mobile station 150. The mobile station 150 is unable to determine if transmit signals are received from the repeater 112 or directly from the base station 102. Thus, a mobile station 150 may determine that it is positioned a distance, R, from the base station 102 when the mobile station is actually positioned the distance, R, from the repeater 112. The mobile station 150 may determine its range from a signal source using, for example, the Pseudo Noise (PN) code transmitted by a Code Division Multiple Access (CDMA) signal source.
In some position determination systems, a latitude, longitude, and time calibration for the point of transmission are used in determining the position of the mobile station 150. Ambiguity in the source of a signal creates problems for position determination solutions. The position determination system may determine an inaccurate location of the mobile station 150, or the ambiguity in signal source may result in an inability of the position determination system to locate the mobile station 150.
What is desirable is a new repeater that augments the signal received from the base station before retransmitting it. It is desirable for a mobile station to be able to determine whether a base station or a repeater transmitted the signal. Additionally, if a repeater transmitted the signal, the mobile station should be able to identify a particular repeater where more than one repeater is used with the same base station. The augmented repeater signal should allow a mobile station, or some other receiver, to resolve signal source ambiguity in order to support position determination.